Speaker
Roy Alexander Tinguely
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1071.pdf
Status of high-electron-temperature experiments at GDT mirror trap
A. G. Shalashov1,2, P. A. Bagryansky1, E. D. Gospodchikov1,2, L. V. Lubyako1,2,
V. V. Maximov1, V. V. Prikhodko1, V. Ya. Savkin1, E. I. Soldatkina1,
A. L. Solomakhin1, and D. V. Yakovlev1
1
Budker Institute of Nuclear Physics SB RAS, Novosibirsk, Russia
2
Institute of Applied Physics RAS, Nizhny Novgorod, Russia
The paper summarizes results of experiments on electron cyclotron resonance plasma
heating (ECRH) and related issues at the axially symmetric large-scale gas-dynamic
magnetic mirror trap GDT in the Budker Institute (Novosibirsk, Russia). Previously we
reported on plasma discharges with extremely high temperature of bulk electrons in this
machine – the on-axis electron temperature 600–700 eV at the plasma density about
0.7×1019 m-3 was achieved and values of Te > 900 eV were observed in select individual
shots – more than a threefold increase with respect to previous experiments both at GDT
and at other comparable devices [1]. The breakthrough is made possible by application of
0.7 MW / 54.5 GHz ECRH in addition to standard 5 MW heating by neutral beams.
Through its significant impact on plasma parameters, ECRH poses a threat to the subtle
magnetohydrodynamic equilibrium of plasma confined in a magnetic mirror machine. In
particular, when the microwave power was focused in a narrow near-axial plasma region
thereby leading to a highly peaked radial profile of the electron temperature, the duration of
effective heating was always limited to about 0.6 ms; later on, the flute instability
developed preventing further absorption of microwaves. Recently, we introduce a new
technique which counters such detrimental effects of microwave heating and enables to
maintain high electron temperature for the whole duration of plasma discharge. We show
that a value of on-axis electron temperature up to 450 eV at plasma density 1.2×1019 m-3
can be supported steadily for more than 1 ms limited only by available heating and
magnetic confinement systems. Stable high-temperature discharge regime offered a unique
opportunity to validate experimentally the gas-dynamics confinement mechanism in a new
realm of parameters.
[1] P. A. Bagryansky, A. G. Shalashov et al., Phys. Rev. Lett. 114 205001 (2015).
